The leak would be internal to the plenum. Here's another thing, leave the tester on over night and see what it reads in the morning.

I asked another question in my post above... Did you replace the internal fuel lines when you replaced the CPI spider? A weeping leak on the 'nut kit' will bleed pressure off VERY slowly.

 

I did not replace the "nut kt" because there was no washing or pooling on the drivers side of the intake plenumn. the fuel pressure regulator is new with the spider, even if the nut kit were to be bleeding off very slowly with there being no pressure loss within a 10-15 minute time period could this still be an issue?